(1) Field of Invention
(2) Description of the Prior Art
A conventional hand tool for driving a fastener head is experienced a problem that the driving surfaces of the jaws for an open-end wrench, for example, cannot precisely matched with the straight sides of the fattener head so that when rotating the wrench, the corners of the fattener head is rounded off. Some wrench has special design to the configuration of the driving surfaces and can bite the rounded fastener head and successfully drive the rounded fastener head. However, these special designed wrench causes marring to the normal fastener head and sharpens the sides of the fastener head. After the fastener is loosened, the user rotates the fattener out form threaded rod and the user's fingers might be cut by the sharp sides of the fastener head. Some of these designs known to applicant are disclosed in U.S. Pat. No. 5,860,339, U.S. Pat. No. 6,009,778, U.S. Pat. No. 5,148,726, U.S. Pat. No. 5,117,714, U.S. Pat. No. 5,074,171, and U.S. Pat. No. 6,145,414.
U.S. Pat. No. 5,406,868 and U.S. Pat. No. 5,381,710 disclose a wrench with open-end and the two jaws each have a rounded ridge extending therefrom so as not to mar the sides of fastener heads. Nevertheless, when driving a rounded fastener head, an assistance tool such as a pair of locking pliers have to be used to hold the fastener.
The present invention intends to provide a driving surface configuration for a hand tool and each driving surface includes a contacting area and two yielding areas, the contacting area protrudes from the driving surface and includes a contact portion and two notches, wherein the contact portion matches with sides of normal fastener and the notches effectively bite the rounded fastener.